Smart Structural Elements Research Articles

Suboptimal distributed state-feedback control of semi-active vibrating systems

A novel semi-active control method for mitigating structural vibration is studied. The method relies on distributed state information patterns and the solution to a suboptimal control problem that aims at replicating the switched structures of the optimal open-loop stabilizing controls. The optimality conditions and the method of solution of the suboptimal problem are discussed. The performance of this method is examined by means of numerical experiments performed for a double cantilever system equipped with a set of semi-active elastomers with controlled viscoelastic properties. The experiments were carried out for different controller architectures and a series of initial conditions. In terms of the assumed objectives, the proposed distributed control strategy significantly outperforms the passive damping strategies and is competitive with a standard centralized control. The proposed approach is general to a class of bilinear control systems concerned with smart structural elements. The practical aspects of the designed distributed controller are highlighted.

Decentralized stabilization of semi-active vibrating structures

Abstract A novel method of decentralized structural vibration control is presented. The control is assumed to be realized by a semi-active device. The objective is to stabilize a vibrating system with the optimal rates of decrease of the energy. The controller relies on an easily implemented decentralized switched state-feedback control law. It uses a set of communication channels to exchange the state information between the neighboring subcontrollers. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of elastomers with controlled viscoelastic properties. In terms of the assumed objectives, the proposed control strategy significantly outperforms the passive damping cases and is competitive with a standard centralized control. The presented methodology can be applied to a class of bilinear control systems concerned with smart structural elements.

Seismic behaviour of repaired superelastic shape memory alloy reinforced concrete beam-column joint

Large-scale earthquakes pose serious threats to infrastructure causing substantial damage and large residual deformations. Superelastic (SE) Shape-Memory-Alloys (SMAs) are unique alloys with the ability to undergo large deformations, but can recover its original shape upon stress removal. The purpose of this research is to exploit this characteristic of SMAs such that concrete Beam-Column Joints (BCJs) reinforced with SMA bars at the plastic hinge region experience reduced residual deformation at the end of earthquakes. Another objective is to evaluate the seismic performance of SMA Reinforced Concrete BCJs repaired with flowable Structural-Repair-Concrete (SRC). A <TEX>$\frac{3}{4}$</TEX>-scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading, and subsequently repaired and retested. The joint was selected from an RC building located in the seismic region of western Canada. It was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour under reversed cyclic loading of the original and repaired joints, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation, requiring a minimum amount of repair, even after a large earthquake, proving to be smart structural elements. It was also shown that the use of SRC to repair damaged BCJs can restore its full capacity.

Vibration Control of Spacecraft Box Structures Using a Collocated Piezo-Actuator/Sensor

The problem of vibration control in box-type structures is examined by inclusion of piezo-electric smart structural elements. The box is modeled as a system of joined plates in which both extensional and bending deflections are incorporated. By collocating the sensor and actuator elements, the input–output property of passivity is achieved independent of the number of modeled modes and details such as frequencies and mode shapes. Robust vibration control is achieved by designing a strictly positive real dynamic compensator for the system.

Optimal location of collocated piezo-actuator/sensor combinations in spacecraftbox structures

The problem of actuator/sensor location is examined for the inclusion ofpiezoelectric smart structural elements in box-type structures. The box is modeledas a system of joined plates in which both extensional and bending deflections areincorporated. A location criterion is developed which is based on the dampinginjected into the first few modes by a simple constant gain feedback. It is foundthat the central regions of each face which avoid the edges and cornersoffer the most promising sites for collocating piezo-actuators and sensors.

855 形状記憶合金の微視的考察に基づく一次元内部ループモデル

A specimen-based one-dimensional model of SMA was derived from the grain-based micromechanical model we proposed under Reuss assumption, where the transformation criterion was used that the phase transformation was assumed to occur when a driving energy was equal to a required transformation energy. Moreover to describe inner loops the shift-skip model was proposed based on micromechanical consideration, where the required transformation energy was shifted or skipped at the turn volume fractions. To verify the validity of the proposed model, comparison of small-strain loops of stress-strain relationship between experiment and calculation based on the model was performed. Here an exponential function was applied to the required transformation energy function from the experimental observation. The result showed the model could capture the small-strain loops quantitatively. That suggests that this model can be applied to analyzing SMA or designing smart structural elements including SMA.

Stress analysis of piezoceramic cylinders

The development of versatile analytical methods for analysis of smart structural elements is becoming increasingly important. Solid and thick cylinders are among the most common forms of structural elements used in practical applications. In this paper, the coupled electroelastic equations governing the axisymmetric elastic and electric fields of a long annular piezoceramic cylinder are solved by applying Fourier integral transforms. The ceramic is assumed to be hexagonally symmetric about or polarized along the axis of the cylinder. Explicit analytical solutions are presented for all of the components of the elastic and electric fields. Solutions for a solid cylinder subjected to a radial ring load and a ring electric charge are presented. Solutions for a band load and an electric charge are also presented, and the singularities of the coupled electroelastic fields are examined. Selected numerical solutions for cylinders made out of three different piezoceramics and subjected to a load and an electric charge are presented to demonstrate the salient features of the coupled fields. The general solutions presented in this paper are very useful in the study of load-transfer mechanisms, active regions, and the micromechanics of cylindrical fibre-reinforced composite elements containing piezoceramic sensors/actuators. The present solutions can also be used in the boundary element analysis of cylindrical smart elements.